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EarthCache

A "Gorge"ous Look at Geology: Abelmans Gorge

Hidden : 10/27/2008
In Wisconsin, United States
Difficulty:
1.5 out of 5
Terrain:
2 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:

A visit to this amazing gap in a quartzite syncline will leave you breathless from the views. Explore an area that is considered one of Wisconsin’s most important sites for learning the geological story of our region.





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Abelman’s Gorge has been cut by the Baraboo River through the layers of geological history; metamorphic Baraboo quartzite, Cambrian sandstone and conglomerates. The locale is famous for its exposures of uncomformity between the ancient quartzite and overlying sandstone, making it a “must see” destination for amateur and professional geologists alike.

You will hike from the parking area along the north face of the cliffs, following the course of the Baraboo River to a point where natural springs arise from the rocks and flow into the Baraboo. All of this is set against the backdrop of the towering weathered cliffs, which create a cool moist habitat harboring plants typical of northern Wisconsin. If you wish, you are encouraged to continue along the trail and visit the south facing portion of the cliff, where an old quarry operation exposes more boldly the geological story. To complete the EarthCache requirements, you need only travel as far as the rock springs. At all times, rock climbing is prohibited in this state natural area.

Early in Wisconsin history, the nearby town of Rock Springs was named “Abelmans,” taking the name of the first settlers who farmed here. Earlier than that, a story of drama and change unfolded in this area, which is also known as the “Upper Narrows.” Today, this state natural area honors the Abelmans with their name.

The Geologic Story

This state natural area is often used for study by students of geology. No where else does one have the chance to see the geomorphologic story so clearly displayed due to the world famous unconformities. For our purposes, this story begins about a billion years ago, in late Precambrian times, with the deposition of many hundreds of feet of clean quartz sand. Over the eons, these sand layers were transformed into Baraboo quartzite, a metamorphic rock, one which has undergone change due to intense forces such as heat, or in this case, pressure.

This quartzite, due to its angular grains, is very brittle and prone to fracture. This fracturing explains the presence of the talus field seen at the base of the cliff here, from which the spring arises. The stone is characteristically pink or lavender, due to small amounts of iron oxide, and ripple marks can sometimes be observed, evidence of its early life in a marine environment.

Sometime after the recession of this ancient sea, forces caused folding and uplifting of the area, resulting in a tilted syncline. Further erosion from the weathering and marine environment can be seen by careful examination.

Enter the Ice Age, the Cary ice sheet advancing to just short of this area. As the glacier began to melt rather abruptly, the waters rushed through, creating several gaps within the Baraboo Range, leaving in their wake the piles of fractured talus and carrying conglomerates from further north, resulting in the landscape before you today. The nearby gap, called “Abelman’s Gap” or the “Upper Narrows,” provides the opening through which the Baraboo River enters the central valley of the Baraboo Hills. The small spring arising from the rocks at the listed coordinates travels and joins the river nearby.

To claim credit for this EarthCache:

Task 1: At the listed coordinates, you will discover a small spring arising from the rocks on your path. You have two choices here. Take a water temperature reading, or measure the flow rate by filling a container of known volume and discovering how long it takes to fill.

Task 2: Estimate the height of the canyon wall to the southeast behind the source of the spring.

Task 3: Not required, but appreciated. Wander the area, without rock climbing, to look for an interesting story in the rocks here. There are two parts to this task. First; take a photo of yourself (or your GPSr if solo caching without a tripod), studying this story. Show action in these photos, as opposed to the standard “face the camera and hold up your GPSr” shot. Post this photo in your “found it” log.

Second, email us your hypothesis about the forces that caused this feature, along with your answers to Task 1 and Task 2.

Any logs by finders who do not send us the answers to the above questions within one week will be deleted.

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References

The Physical Geography of Wisconsin, Lawrence Martin: University of Wisconsin Press, 1965

"Wisconsin Geological Localities," Steven Dutch, University of Wisconsin-Green Bay

http://www.uwsp.edu/geo/projects/geoweb/participants/dutch/geolwisc/geostops/gstopind.htm

Ancient Rocks and Vanished Glaciers: A Natural History of Devil's Lake State Park, Kenneth L. Lange: Worzalla Publishing Company, 1989

The Geocache Notification Form has been submitted to Thomas Meyer of the Wisconsin DNR. Geocaches placed on Wisconsin Department of Natural Resource managed lands require permission by means of a notification form. Please print out a paper copy of the notification form, fill in all required information, then submit it to the land manager. The DNR Notification form and land manager information can be obtained at: http://www.wi-geocaching.com/hiding

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Inventory

There are no Trackables in this cache.

 

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75 Logged Visits

Found it 67     Didn't find it 3     Write note 4     Publish Listing 1     

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Current Time:
Last Updated: on 10/12/2014 6:21:02 PM Pacific Daylight Time (1:21 AM GMT)
Rendered From:Unknown
Coordinates are in the WGS84 datum